1. Field of the Invention.
This invention relates to orthotic protective devices for the ankle joint and in particular to devices which are meant to permit dorsiflexion and plantar-flexion of the foot while protecting against inversion or eversion of the foot.
2. Description of the Prior Art
The layman generally speaks of the ankle as the two prominent bony protuberances at the base of the lower leg. Referring to FIGS. 7-11, these protuberances are the expanded inferior or lower extremeties of the tibia 1, which is the large weight-bearing bone of the leg, and the fibula 2, a slender bone which lies parallel to the tibia and does not participate in weight-bearing. The tibia is nearer the medial plane of the body (a vertical plane through the erect body at the midline from behind to front), and is said to be "medial" to the fibula, which, conversely, is farther from the medial plane and is said to be "lateral" to the tibia. The two protuburances are called the medial malleolus 3 (tibia) and the lateral malleolus 4 (fibula). Anatomically the lower or distal end of the tibia rests on the ankle bone 5 called the talus, which in turn rests on the upper surface of the heel bone 6 called the calcaneous. The talus is held between the two malleoli, and with them and the lower end of the tibia, forms the ankle joint, indicated generally by the reference numeral 7.
The ankle joint 7 is of the hinge type, its form being that of a mortise and tenon, the box-like mortise being constructed superiorly by the distal surface 8 of the tibia, medially by the lateral aspect 9 of the medial malleolus 3, and laterally by the medial side 10 of the lateral malleolus 4. Posteriorly the socket between the tibia and fibula is completed by a ligament (the transverse tibiofibular ligament), not shown. The tenon of the joint is the upper articulating body 11 of the talus (the "trochlea").
Hinge movement at the ankle joint takes place around a transverse axis on a level with the tip of the lateral malleolus 4 and slightly below the level of the medial malleolus 3. In "dorsiflexion" the foot is drawn upwards, the trochlea 11 of the talus rotating backwards in the tibio-fibula socket; movement in the opposite direction is "plantar-flexion" (see FIG. 11). The trochlea narrows from front to back and is most snugly grasped between the malleoli in full dorsiflexion and least snugly held in full plantar-flexion.
The joint is surrounded by a joint capsule which, in correspondence with the requirements of free hinge movement at the ankle, is very weak in front and behind. The stability of the joint is given at the sides by the collateral ligaments. These are an exceedingly strong deltoid ligament 12 on the medial side radiating down from the medial malleolus 3 and, on the lateral side, are three separated ligaments originating from the lateral malleolus 4. The deltoid ligament on the medial side is so strong that the medial malleolus to which it is attached more commonly breaks than the ligament ruptures. On the lateral side, the three separate lateral ligaments (the anterior talofibular 13, the calcaneofibular 14, and the posterior taIofibular 15) are much less strong connections than the deltoid ligament.
Because the joint ligaments are much weaker to the front and laterally, an ankle sprain is almost always due to an involuntary inversion or twisting of the foot inwardly, wrenching the trochlear of the talus outwardly in a lateral direction (often combined with a forward displacement), resulting in strain, tearing or rupture of one or more of the lateral ligaments (see FIG. 8). Far less common than inversion injury is ankle injury due to eversion or twisting of the foot outwardly, but impact or crush injury to the medial malleolus, such as caused by the footpegs of a motorcycle, can chip off a portion of the medial malleolus, tearing some of the deltoid ligament and, if the foot is everted strongly, also may fracture or break the lower part of the fibula. Either inversion or eversion injury, with displacement of the trochlear body, often pinches and mashes the synovial membrane of the ankle joint and rips associated vasculature, causing extensive swelling of the joint and foot due to fluid exudation. Once sprained, the ligaments seem never as strong as before, and the joint is more liable to a recurrence of the injury.
The time honored treatment of the sprained or fractured ankle is to immobilize it in a cast, usually split to avoid strangulation of the limb from the swelling. This fixes the joint to allow the ligaments and other injured tissues to mend. After a number of weeks the cast is removed and an orthotic device or aid usually is fitted or applied to permit recuperative walking with plantar-flexion and dorsiflexion while restricting inversion or eversion of the foot. This treatment and an orthotic device for that purpose is described in U.S. Pat. No. 4,280,489 issued to Johnson on July 28, 1981, marketed as the AIR-STIRRUP ankle brace by Aircast Incorporated, Summit, N.J. This device includes a U-shaped stirrup formed by a base to which are attached two vertical side members extending from the base to form sidewalls for a pair of air bags placed adjacent the lateral and medial sides of the leg and foot all the way to the stirrup base, with VELCRO closures being used to maintain the sidewalls and airbags against the sides of the legs. The device is worn in a laced shoe for effective resistance of inversion or eversion The patent describes forming the sidewalls with a thermoplastic material and contemplates replacing where the sidewalls neck down to join the base with a short flexible webbing to avoid fractures at the joinder caused by vigorous use. The marketed AIR-STIRRUP device attaches a loop backed web to VELCRO hook patches on the inside of the sidewalls and passes the web through a slot at the bottom of each sidewall then through the heel pad formed by a doubled-over VELCRO hook fabric to permit vertical down adjustability of the heel pad relative to the ankle recesses formed in the sidewalls.
Another type of orthotic device, exemplified by U.S. Pat. No. 4,510,927, issued to Peters on Apr. 16, 1985, and U.S. Pat. No. 4,517,968, issued to Greene et al on May 21, 1985, employs a rigid or semi-rigid heel cup or stirrup which supports uprights at a pivot mount proximate the transverse axis of rotation of the ankle joint. Foam pads are provided for comfort between the leg and the uprights and typically VELCRO closures or straps are used over the uprights for easy application.
The Peters patent contains an informative discussion of the prior art for orthotic ankle braces, to which reference is made. In addition to the devices described in the Peters patent, other devices allowing dorsiflexion and plantar-flexion which may be mentioned include U.S. Pat. No. 487,492 to Pugsley, issued Dec. 6, 1892, and U.S. Pat. No. 1,465,233 to Posner, issued Aug. 14, 1923, both disclosing an unitary ankle support open at the front and rear; U.S. Pat. No. 2,830,585 to Weiss, issued Apr. 15, 1958, and U.S. Pat. No. 4,440,158 to Shapiro, issued Apr. 3, 1984, each show lace-up ankle supports closed at the rear.
Because the once-sprained or fractured ankle is weaker after injury, and to prevent recurrent or initial sprains, some high schools and most college and professional teams in sports such as football or basketball prophylactically tape the ankle joint of each leg of every athlete before the athlete is allowed on the playing court or field. The tape wrap of the joint is intended to brace the joint against inversion or eversion. The practice of taping is expensive and, while endured, not especially liked. Skilled athletic trainers or similarly trained personnel are needed to perform the taping; their time with its expense and the time of the athletes is consumed to apply the tape and then take it off, before and after every athletic event, whether practice or game days. The tape obviously is not reusable, and in the aggregate, day in and day out, large quantities of not inexpensive tape are consumed. Repetitive applications and removal of the tape can and often does involve discomfort and skin irritation to the athlete. Dorsiflexion and plantar-flexion often are compromised. Moreover, taping is not wholly effective, because under practice or game conditions with intense perspiration and vigorous movement of the limbs at the ankle joint during running, jumping and change of direction, the tape tends to loose its grip. The frequency of ankle injuries in sports even with taping is testimony enough to the limited efficacy of taping. Still, it has remained the only widespread prophylactic solution to the problem.
Particularly for the injured athlete seeking to get back into playing time, efforts have been made to use variations of the orthotic devices mentioned above to provide additional support, with or without taping. The more effective such orthotics generally are lace-up supports with lateral stays and stiffeners, sometimes to mid-calf length, over which the shoe is laced: sort of a legging or toeless and heel-less boot within a shoe. Devices of the foot-cup pivoting type generally are too cumbersome and mechanically restrictive for athletic use. The AIR-STIRRUP device has been tried but found unsatisfactory for athletic use (the VELCRO closures and straps give way and slip with use and wear; the lining of the airbag is a slick plastic surface which does not grip the athlete's sock or leg, especially when wet with perspiration; and fitted within a shoe, the deep sidewalls of the device engage the inside surface of the shoe sole and are lifted up and let down or pivot back and forth with movement of the foot in the shoe).
Even while tolerated, these supplemental devices generally are not favored by the athlete, because, depending on the device, they are ineffectual, bulky, uncomfortable, add tiring weight to the limbs, particularly the lace-ups when wetted with perspiration, and are perceived by the wearer as compromising and slowing athletic performance, costing the athlete an edge against his or her competitor. Moreover, the devices are relatively expensive.